VSS/VSL no cdp enable - why?

[Michael Berry]

I'm wondering if anyone can explain the underlying technical reason why cdp is disabled on VSL links without an option to re-enable.  I'm looking for a technical reason - is there some type of conflict that is being avoided and why does it only apply to cdp...

[agapitca19]

Michael,

I was wondering too when configuring our 6807s for VSS. Maybe below will give some inputs.  

http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Campus/VSS30dg/campusVSS_DG/VSS-dg_ch2.html

VSL Characteristics

The VSL port channel is treated as an internal systems link. As a result, its configuration, resiliency, mode of operation, quality of service (QoS), and traffic load sharing follow a set of rules that are specific to VSL. This section covers configuration requirements relating to those rules. The logical port channel and its member link both have distinct sets of restrictions.

VSL protocol(VSLP) runs VSL, that follows its own sets of rules to manage the link.

http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-virtual-switching-system-1440/109547-vss-best-practices.html

VSS Terminology

• Virtual Switch Link (VSL)—A special port channel required to bundle two physical switches into one virtual switch.

• VSL Protocol (VSLP)—Runs between active and standby switch over the VSL, and has two components: LMP and RRP

  • Link Management Protocol (LMP)—Runs over each individual link in VSL

  • Role Resolution Protocol (RRP)—Runs on each side (each peer) of the VSL port channel

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